The Communist Party of the Soviet Union (CPSU), at some points known as the Russian Communist Party, All-Union Communist Party and Bolshevik Party, and sometimes referred to as the Soviet Communist Party (SCP), was the founding and ruling political party of the Soviet Union. The CPSU was the sole governing party of the Soviet Union until 1990 when the Congress of People's Deputies modified Article 6 of the 1977 Soviet Constitution, which had previously granted the CPSU a monopoly over the political system. The party's main ideology was Marxism–Leninism.

The Soviet Union, officially the Union of Soviet Socialist Republics (USSR), was a transcontinental country that spanned much of Eurasia from 1922 to 1991. It was a successor state to the Russian Empire that was nominally organized as a federal union of fifteen national republics, the largest and most populous of which was the Russian SFSR; in practice both its government and economy were highly centralized until its final years. As a one-party state governed by the Communist Party of the Soviet Union, it was a flagship communist state.